ES2386301T3 - Synthetic grass and corresponding manufacturing procedure - Google Patents

Abstract

A synthetic-grass covering, usable, for example, for making artificial pitches for sports activities, comprises: - a substrate made of sheet material (10, 12, 20); and - filiform formations (14), implanted in the aforesaid sheetlike substrate (10, 12, 20) so as to present a looped part (16) that extends up against one of the surfaces of the sheetlike substrate (10, 12, 20) and lateral branches (18) that extend in order to simulate the grassy sward of natural turf from the opposite surface of the sheetlike substrate (10, 12, 20). The substrate made of sheet material (10, 12, 20) comprises a pad (10) with coupled thereto a layer (12) made of heat-meltable material, and the filiform formations (14) are also made of heat-meltable material, with the aforesaid looped parts (16) that extend in an area corresponding to the layer (12) made of heat-meltable material, heat-welded to the aforesaid layer.

Description

Synthetic grass and corresponding manufacturing procedure.

The present invention relates to synthetic (or "artificial") grass coverings.

Synthetic grass coverings have been used for some time now, in particular to provide areas of green areas for urban decoration and similar services, for areas surrounding swimming pools, and, in general, to replace the natural grass covering in all those conditions in which the placement and maintenance of a natural grass cladding can be critical. The use of synthetic grass coverings has received new momentum in recent times in order to provide coverings for sports facilities, for example, football fields. The corresponding bibliography is extremely extensive, as demonstrated, at the patent level, by documents such as: US-A-3 731 923, US-A-4 337 283, US-A-5 958 527, US- A-5 961 389, US-A-5 976 645, JP-B-32 53 204, JP-A-10037122, DE-A-44 44 030, EP-A-0 377 925 and EP-A-1 158 099

In particular, from the last mentioned document, which is owned by the owner of the present application, a synthetic turf structure is known, comprising a sheet-like substrate with a plurality of filiform formations extending from the substrate for simulate a layer of natural grass grass and a particulate filler material, or filler, dispersed between the filiform formations to maintain the filiform formations themselves in a substantially vertical state. Specifically, the above synthetic turf coating is characterized in that the particulate filler material (filler) is constituted by a substantially homogeneous mass of a granular material chosen from the group consisting of polyolefin-based materials and vinyl polymer-based materials.

Further advantageous developments of the above solution are described in EP-A-1 319 753, EP-A-1 375 750, EP-A-1 371 779, as well as EP-A-1 486 613, and new in European Patent Application No. 05425957.7, all such documents having been submitted in the name of the present applicant.

Over the last few years, as regards the application to the construction of lawn coverings for sports facilities, the innovation activity has mainly been directed to the characteristics and modalities of distribution of the stuffing or filling material.

Taken together, less attention has been paid to the characteristics of the filament used to make such filiform formations. In this regard, reference may be made, for example, to EP-A-0 259 940, which describes, instead, the possibility of using, in a synthetic turf coating, a filament obtained with the coextrusion of polymeric materials of different composition, in particular with different coefficients of friction.

A solution widely used to manufacture the aforementioned filiform formations considers resorting to a filament having a base of plastic material, such as polyethylene. The material in question is initially laminated to form a sheet of, for example, 200-300 microns thick. The sheet is then subjected to a cutting operation, which divides the sheet into a larger number of strips of smaller width (for example, 10-20 mm). The cutting operation is usually followed by one or more longitudinal stretching operations, as well as possible fibrillation operations.

An alternative technique (“single-wire” technique) considers, instead, that a material that originates as a

Single thread from a spinning nozzle undergoes a longitudinal stretching process.

Regardless of the technique adopted to manufacture it, the filament thus obtained is wound on coils. The coils in question are then used to feed work stations that form the basic structure of a synthetic turf coating of the type described above, that is, with the filiform formations extending from a sheet-like substrate. Such workstations normally operate with known techniques that resemble bolting techniques or the like.

In particular, these techniques have the objective of "implanting" in the sheet-like substrate (which is continuous or

substantially continuous, for example, because it is provided with drain holes) filament formations having a general U-shaped configuration. Each formation basically constitutes a kind of tuft with a loop part that passes under the substrate, and two lateral branches that extend vertically above the substrate simulating the blades of grass. In the case of the single thread, instead, the plume is made up of four, six or eight strands or "blades", depending on the thickness and / or width of the blade itself.

The fibrillation operation (performed either before or after implantation in the substrate) presents

basically the objective of "providing more volume" to the filament and therefore to the plume formed with it. He

Plume is usually made up of one or more threads that tend to widen so that the individual tuft of synthetic grass seems denser and therefore more similar to a plume of natural grass. In the case of elements of the blade type, the blades subjected to fibrillation are each divided into several strands.

Although altogether they are satisfactory, these traditional techniques leave room for further improvements with respect to various aspects.

An important aspect concerns the anchoring of the filiform formations to the sheet-like substrate.

A widely used technique considers applying, on the underside of the substrate (that is, the one that must be oriented downwards when laying the synthetic grass covering), an aqueous dispersion of latex, such as SBR latex. The solution in question is dried and the latex, so to speak, plug or "block" the openings for the passage of the filiform formations through the sheet-like substrate. However, it cannot be said that the anchoring action thus achieved is satisfactory to the extent that filiform formations can be torn off with relative ease.

Other solutions (such as those described in documents US-B-6 338 885 or US-B-6 723 412) consider the application, once again on the lower side of the substrate, of strips of adhesive tape or material adhesive that must more firmly anchor the loop parts of the U-shaped configurations mentioned above.

An important drawback of this technique derives from the fact that the strips mentioned above form a groove on the lower side of the filiform substrate, which no longer rests completely on the underlying foundation and ends up adopting marked directional characteristics with respect to tensile strength. mechanical

The last mentioned aspect acquires a particular importance in view of the fact that the sheet-type substrate of the synthetic grass cover must be able to perform an effective dimensional stabilization action of the synthetic grass cover, an action that in general is not performed satisfactorily by layers of sheets of a traditional type, for example, with a base of polyester and / or polypropylene sheets.

More specifically, the invention relates to a synthetic grass covering according to the preamble of claim 1, which is known, for example, from JP 06 116 155. Substantially similar arrangements are known, for example, from JP documents 11 291 308 or US-A- 4 705 706.

Then, the main objective of the present invention is to improve the existing synthetic turf coatings with respect to both aspects mentioned above, that is, anchoring of the filiform formations to the substrate and the stabilizing action of the synthetic turf coating by the type substrate sheet.

According to the present invention, this objective is achieved thanks to a synthetic grass covering having the characteristics specifically mentioned in claim 1 below. The invention also relates to a corresponding method as mentioned in claim 11.

The claims form an integral part of the technical description provided herein in relation to the invention.

The invention will now be described, merely by way of non-limiting example with reference to the figures on the attached sheet of drawings, in which:

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Figures 1 to 4 illustrate successive steps of a possible method of constructing a synthetic grass covering of the type described herein;

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Figure 5 illustrates a possible variant embodiment of the synthetic grass covering illustrated in Figures 1 to 4; Y

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Figure 6 is a schematic illustration of a synthetic turf coating of the type described herein integrated with a padding of granular material, in the typical position of placement and final use.

In Figure 1 of the attached sheet of drawings, reference number 10 designates a support having a thickness substantially equal to 3 mm and a weight per unit area substantially equal to 300 g / m2, constituted with a polyester base or PET

In the context of the invention, a thickness of between 1.5 mm (weight per unit area: 150 g / m2) and 4 mm (weight per unit area: 400 g / m2 may advantageously be used in any case) ) and / or any polyolefin based material.

The term "support" is intended herein to indicate a sheet material obtained from threads, filaments or fibers associated with each other such that:

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qualities of mechanical resistance to tensile forces are provided to the layer of material, to cause the support 10 not to tear under the normal conditions of use mentioned below; Y

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empty spaces such as to allow a firm anchoring of the support 10 to an additional cover layer 12 (and possibly a mesh 20), described in more detail, are present in any case, between the threads, filaments or fibers. then.

For example, the support 10 can be manufactured in the form of:

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a simple woven textile material (to present a weft and a warp),

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a knitted textile material,

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a non-woven textile material or a felt, possibly stabilized with weft padding.

Of course, the embodiments described above can also be combined with each other, considering, for example, the formation of the support 10 in the form of a non-woven fabric subsequently padded / padded with a weft and warp pattern.

When the above feature is no longer intrinsically derived from the constituent material (as in the case of polyester or PET), the support 10 can be treated with known agents to make it hydrophobic.

Figure 2 illustrates the coupling of the support 10 to the layer 12, as mentioned above.

The layer 12 is constituted by a thermoplastic material (hence hot melt), usually by a polyolefin-based material, such as, for example, polyethylene.

The coupling of the layer 12 to the support 10 can be obtained with various techniques known per se.

For example, the layer 12 of material can be coupled to the support 10 by hot pressing. Alternatively, the layer 12 can be extended on the support 10. Alternative techniques comprise spraying the layer 12 of the material in a liquid or molten state with subsequent consolidation, and connection obtained by the application of ultrasound.

The connection is preferably obtained in a continuous manner on all the facing surfaces of the support 10 of the layer 12. Less preferred solutions consider that the connection is made only on parts of the facing surfaces (for example, with a knitted or sewn pattern) and / or with a mechanical type connection, for example, by padding or the like.

In an embodiment that is particularly preferred (but not imperative in itself), it is considered that, as schematically represented in Figure 5, against the layer 12 is fixed (preferably coupled to the layer 12 applied on the support 10 , being carried out in a single step) a stabilizing mesh 20, constituted, for example, by a new mesh made of thermoplastic and therefore hot melt material, and preferably of a polyester with a thermosetting and stabilized mesh, with a weight per unit area between 30 g / m2 and 150 g / m2 (preferably substantially equal to 80 g / m2).

The combined laminated material (support 10 plus layer 12 and, if present, mesh 20) thus obtained is then used as a sheet substrate for the construction of a synthetic grass covering according to the modalities (known in themselves) to which it is made reference schematically in figure 3.

The combined laminate 10, 12 (and possibly 20) is fed to equipment (not illustrated, but of a type itself widely known in the synthetic turf coatings manufacturing sector) that substantially resembles a machine stiffened

The equipment in question implants in the sheet-type substrate 10, 12 (and possibly 20) wire formations 14 which have a general U-shaped configuration. Each formation basically constitutes a kind of tuft with a loop part 16 that passes under the substrate 10, 12 and two branches 18 that extend vertically above the substrate 10, 12 simulating blades of grass.

In later stages of the synthetic turf cladding manufacturing process (stages not illustrated herein, also because in themselves they are not important for the purposes of understanding and implementing the invention), the two aforementioned branches 18 can be subjected to treatments additional, for example, fibrillation, curly, etc. designed to cause the threads that constitute them to reproduce in a more faithful way the appearance of natural grass grass layer.

The implantation operation of the filiform formations 14 is obtained in such a way that the looped portions 16 are in contact with the layer 12 (and the mesh 20, if present), while the formations 18 protrude with respect to the general plane of the substrate 10, 12 on the side on which the support 10 is fixed.

The synthetic grass covering structure thus obtained is then subjected to the action of a heating element H (for example, a heated plate or roller, which preferably works in contact) according to the modalities represented schematically in Figure 4, the purpose being produce a localized fusion (with consequent mutual welding) of the looped portions 16 and of the areolas of the layer 12 (and of the mesh 20, if present) in a corresponding area in which the looped portions 16 extend.

Welding is obtained thanks to the fact that both the material of the filiform formations 14 (and therefore of the looped parts 16) and the material of the layer 12 (and of the mesh 20, if present) are made of material thermoplastic, therefore hot melt and heat sealable. For this same reason, in a particularly preferred embodiment of the invention, the material of layer 12 is chosen to be the same as the (or at least substantially similar to) the material constituting the filiform formations 14.

As already mentioned, polyethylene constitutes a preferable choice from this point of view. The choice of polyethylene allows in fact to obtain a homogeneous and intimate weld, applying on the lower side of the structure represented in figure 3 temperatures in the range of 110 ° C to 200 ° C, according to the application rate / time, therefore without any risk of induce negative phenomena either in the support 10 or in the parts of the filiform formations 14 designated with 18, which must simulate a layer of natural grass.

The connection by heat welding can be seen immediately in the sense that the filiform formations 14 are connected in a definitive and very firm way to the sheet substrate or sheet type substrate constituted by the support 10 and by the layer 12 (and, if present, by mesh 20).

At the same time, the assembly formed by the support 10 and by the layer 12 (and by the mesh 20, if present) provides the sheet-like substrate of the synthetic grass cover with excellent dimensional stability and tensile strength qualities , to deformation and tear. These qualities manifest themselves almost uniformly in all directions, thus preventing said substrate (and therefore the entire synthetic grass covering) from presenting undesirable characteristics of behavioral directionality.

The fact that the layer 10 has the characteristics of a support of a certain thickness has the beneficial effect of providing "volume" to the synthetic grass covering also in the case in which the latter is not subsequently filled with a granular filling.

The hydrophobicity characteristics of the support 10 also mean that the synthetic grass covering has excellent rainwater drainage qualities, thus avoiding the formation of puddles or soaked areas that could lead to stagnation.

As schematically illustrated in Figure 6, the synthetic turf coating described above

it can be advantageously integrated with "seeding" of a filling material or "filling" 22 constituted by a material

granular, for example, one based on polyolefin (also obviously comprising said term the

called "thermoplastic elastomers").

In an embodiment of the invention which is particularly preferred at this time, the filling material 22 mentioned above is of the type described in EP-A-1 158 099.

Obviously, without prejudice to the principle of the invention, construction details and embodiments may vary widely with respect to what is described and illustrated herein, without thereby departing from the scope of the invention as defined by the appended claims.

Claims (11)

1. Synthetic grass covering comprising:

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a substrate made of sheet material (10, 12, 20); Y

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filiform formations (14), implanted in the aforementioned sheet-like substrate (10, 12, 20) to present a loop portion (16) that extends upward against one of the surfaces of said sheet-like substrate (10 , 12, 20) and some free branches (18) extending from the opposite surface of said sheet-like substrate (10, 12, 20) in order to simulate a layer of natural grass, in which:

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said substrate made of sheet material (10, 12, 20) comprises a support (10), coupled to at least one layer (12) made of hot melt material; Y

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said filiform formations (14) are also made of hot melt material, said parts (16) being in a loop that extend in an area corresponding to said at least one layer (12) made of hot melt material, heat welded to said at least one layer (12) made of hot melt material, characterized in that

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both said loop parts (16) and the areolas of said at least one layer (12) in the areas where said loop portions (16) extend are fused to produce a mutual weld, and

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said support (10) has a thickness between 1.5 mm and 4 mm, preferably approximately 3 mm.

2.

Synthetic grass covering according to claim 1, characterized in that both said loop portions (16) of said filiform formations (14) and said at least one layer (12) made of hot melt material are based on polyolefin.

3.

Synthetic grass covering according to claim 1, characterized in that both said loop portions (16) of said filiform formations (14) and said at least one layer (12) made of hot melt material are based on polyethylene.

Four.

Synthetic grass covering according to any of the preceding claims, characterized in that said at least one layer (12) made of hot melt material has a stabilizing mesh (20) associated therewith, which is also made of a material that is at least partially hot melt, heat welded to said at least one layer (12) made of hot melt material and to said loop parts (16) of said filiform formations (14).

5.

Synthetic grass covering according to claim 4, characterized in that said mesh (20) has a weight per unit area between 30 g / m2 and 150 g / m2, preferably substantially equal to 80 g / m2.

6.

Synthetic grass covering according to claim 4 or claim 5, characterized in that said mesh (20) is a polyester mesh, preferably with thermosetting and stabilized mesh.

7.

Synthetic grass covering according to any of the preceding claims, characterized in that said support (10) has a weight per unit area comprised between 150 g / m2 and 400 g / m2, preferably substantially equal to 300 g / m2.

8.

Synthetic grass covering according to any of the preceding claims, characterized in that said support (10) is made of hydrophobic material.

9.

Synthetic grass covering according to any of the preceding claims, characterized in that said support (10) is subjected to hydrophobicity treatment.

10.

Synthetic grass covering according to any of the preceding claims, characterized in that said support (10) has a structure selected from:

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a simple woven structure;

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a knitted structure;

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a structure of nonwoven textile material;

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a felt structure; Y

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a combination of the above structures, such as a padded felt structure.

11. Method for manufacturing a synthetic turf coating according to any one of claims 1 to 10, comprising the following operations:

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providing said substrate made of sheet material (10, 12, 20); and

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implanting in the aforementioned sheet-like substrate (10, 12, 20) filiform formations (14) with a loop portion (16) extending upward against one of the surfaces of said sheet-like substrate (10, 12 , 20) and free branches (18) extending from the opposite surface of said sheet-like substrate (10, 12, 20) in order to simulate a layer of natural grass,

in which the procedure comprises the following operations:

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forming said substrate made of sheet material (10, 12, 20) in the form of a support (10) coupled to at least one layer (12) made of hot melt material,

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forming said filiform formations (14), which are also made of hot melt material,

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implanting said filiform formations (14) in the aforementioned sheet-like substrate (10, 12, 20), with said loop portion (16) extending in an area corresponding to said at least one layer (12) made of hot melt material, and

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heat welding said portions (16) in a loop of said filiform formations (14) to said at least one layer (12) made of hot melt material causing the melting of said parts (16) in a loop and the areolas of said at least one layer (12) in the areas where said parts (16) extend in a loop.